On Fri, 30.05.14 01:29, Luis R. Rodriguez ([email protected]) wrote:
> I'm cc'ing a few security folks as I'd appreciate review on the ideas here,
> in particular that of a launcher idea on system to replace alternatives on the
> ExecStart= line of a systemd service unit file, alternative ideas are of
> course welcomed. I'm also Cc'ing systemd-devel as this subject was reviewed
> a little while ago with nothing concrete being recommended but instead a few
> options being now archived as possibilities. I'm looking for a bit wider
> review of the approaches and recomendations.
>
> Some general background for non xen folks: old xen requires the launch of
> a daemon which implements supports of the xenstore, which is the database
> that xen uses for information about guests / dom0. There are two supported
> daemons, xenstored (C version) and oxenstored (Ocaml version) but they do the
> same thing. Right now old init lets you override which one you pick through
> an environment variable on /etc/{sysconfig,default}/xencommons, the script
> will use the appropriate on there. Systemd doesn't let you use variables on
> the ExecStart line of a service unit file so alternatives are required.
>
> The reason I'm being very careful here this could set a precedent and at
> least for the launcher idea it'd require the usage of getenv() and execve(),
> and secure alternatives for these (secure_getenv(), execve_nosecurity())
> have either been merged or suggested before for Linux. The systemd discussion
> is only specific to Linux but if we have a launcher we could consider it for
> other supported OSes. All that said I'd like proper review of the security
> implications of *all* strategies but obviously in particular the launcher
> idea. I want to tread carefuly before setting precedents.
You can also just invoke a shell script from ExecStart=. I mean, we try
to deemphesize them in the boot process, but there's nothing wrong with
using shell, if you need to parse shell configuraiton fragments and just
want to execute on ot another program...
That said, I'd certainly make a clean cut and drop support for
/etc/sysconfig from any project I see, earlier rather than later, since
it's just cruft, a bad idea and should really just go away. But then
again, I would also just not do the thing with supporting two
implementations at the same time...
Lennart
--
Lennart Poettering, Red Hat
On Sun, Jun 01, 2014 at 08:15:47AM +0200, Lennart Poettering wrote:
> On Fri, 30.05.14 01:29, Luis R. Rodriguez ([email protected]) wrote:
>
> > I'm cc'ing a few security folks as I'd appreciate review on the ideas here,
> > in particular that of a launcher idea on system to replace alternatives on the
> > ExecStart= line of a systemd service unit file, alternative ideas are of
> > course welcomed. I'm also Cc'ing systemd-devel as this subject was reviewed
> > a little while ago with nothing concrete being recommended but instead a few
> > options being now archived as possibilities. I'm looking for a bit wider
> > review of the approaches and recomendations.
> >
> > Some general background for non xen folks: old xen requires the launch of
> > a daemon which implements supports of the xenstore, which is the database
> > that xen uses for information about guests / dom0. There are two supported
> > daemons, xenstored (C version) and oxenstored (Ocaml version) but they do the
> > same thing. Right now old init lets you override which one you pick through
> > an environment variable on /etc/{sysconfig,default}/xencommons, the script
> > will use the appropriate on there. Systemd doesn't let you use variables on
> > the ExecStart line of a service unit file so alternatives are required.
> >
> > The reason I'm being very careful here this could set a precedent and at
> > least for the launcher idea it'd require the usage of getenv() and execve(),
> > and secure alternatives for these (secure_getenv(), execve_nosecurity())
> > have either been merged or suggested before for Linux. The systemd discussion
> > is only specific to Linux but if we have a launcher we could consider it for
> > other supported OSes. All that said I'd like proper review of the security
> > implications of *all* strategies but obviously in particular the launcher
> > idea. I want to tread carefuly before setting precedents.
>
> You can also just invoke a shell script from ExecStart=. I mean, we try
> to deemphesize them in the boot process, but there's nothing wrong with
> using shell, if you need to parse shell configuraiton fragments and just
> want to execute on ot another program...
I tried this and it didn't work given that systemd expects sd_notify()
to be called from the parent process, in this case the shell script.
Anyway -- time has passed folks and we need to pick something, I really
rather not spend any more time on this series unless a decision is made.
My preference stands as the launcher with getenv() and execve() but I
have also listed all other options available. Please feel free to pick
one but just let me know.
> That said, I'd certainly make a clean cut and drop support for
> /etc/sysconfig from any project I see, earlier rather than later, since
> it's just cruft, a bad idea and should really just go away.
We can use for example something like:
# The RPM way
EnvironmentFile=-/etc/sysconfig/xencommons
# The Debian way
EnvironmentFile=-/etc/default/xencommons
Environment=XENSTORED=oxenstored
And with time this lets us with time get rid of EnvironmentFile.
> But then
> again, I would also just not do the thing with supporting two
> implementations at the same time...
:)
Luis
On Wed, Jun 4, 2014 at 5:31 PM, Luis R. Rodriguez <[email protected]> wrote:
> On Sun, Jun 01, 2014 at 08:15:47AM +0200, Lennart Poettering wrote:
>> On Fri, 30.05.14 01:29, Luis R. Rodriguez ([email protected]) wrote:
>>
>> > I'm cc'ing a few security folks as I'd appreciate review on the ideas here,
>> > in particular that of a launcher idea on system to replace alternatives on the
>> > ExecStart= line of a systemd service unit file, alternative ideas are of
>> > course welcomed. I'm also Cc'ing systemd-devel as this subject was reviewed
>> > a little while ago with nothing concrete being recommended but instead a few
>> > options being now archived as possibilities. I'm looking for a bit wider
>> > review of the approaches and recomendations.
>> >
>> > Some general background for non xen folks: old xen requires the launch of
>> > a daemon which implements supports of the xenstore, which is the database
>> > that xen uses for information about guests / dom0. There are two supported
>> > daemons, xenstored (C version) and oxenstored (Ocaml version) but they do the
>> > same thing. Right now old init lets you override which one you pick through
>> > an environment variable on /etc/{sysconfig,default}/xencommons, the script
>> > will use the appropriate on there. Systemd doesn't let you use variables on
>> > the ExecStart line of a service unit file so alternatives are required.
>> >
>> > The reason I'm being very careful here this could set a precedent and at
>> > least for the launcher idea it'd require the usage of getenv() and execve(),
>> > and secure alternatives for these (secure_getenv(), execve_nosecurity())
>> > have either been merged or suggested before for Linux. The systemd discussion
>> > is only specific to Linux but if we have a launcher we could consider it for
>> > other supported OSes. All that said I'd like proper review of the security
>> > implications of *all* strategies but obviously in particular the launcher
>> > idea. I want to tread carefuly before setting precedents.
>>
>> You can also just invoke a shell script from ExecStart=. I mean, we try
>> to deemphesize them in the boot process, but there's nothing wrong with
>> using shell, if you need to parse shell configuraiton fragments and just
>> want to execute on ot another program...
>
> I tried this and it didn't work given that systemd expects sd_notify()
> to be called from the parent process, in this case the shell script.
Just use exec before the daemon command. I am pretty certain it can be
just like this:
ExecStart=/bin/sh -c "exec $XENSTORED"
xenstored then has the same PID as the sh process, and $NOTIFY_SOCKET
works just fine.
Best,
--
Cameron
On Thu, 05.06.14 02:31, Luis R. Rodriguez ([email protected]) wrote:
> On Sun, Jun 01, 2014 at 08:15:47AM +0200, Lennart Poettering wrote:
> > On Fri, 30.05.14 01:29, Luis R. Rodriguez ([email protected]) wrote:
> >
> > > I'm cc'ing a few security folks as I'd appreciate review on the ideas here,
> > > in particular that of a launcher idea on system to replace alternatives on the
> > > ExecStart= line of a systemd service unit file, alternative ideas are of
> > > course welcomed. I'm also Cc'ing systemd-devel as this subject was reviewed
> > > a little while ago with nothing concrete being recommended but instead a few
> > > options being now archived as possibilities. I'm looking for a bit wider
> > > review of the approaches and recomendations.
> > >
> > > Some general background for non xen folks: old xen requires the launch of
> > > a daemon which implements supports of the xenstore, which is the database
> > > that xen uses for information about guests / dom0. There are two supported
> > > daemons, xenstored (C version) and oxenstored (Ocaml version) but they do the
> > > same thing. Right now old init lets you override which one you pick through
> > > an environment variable on /etc/{sysconfig,default}/xencommons, the script
> > > will use the appropriate on there. Systemd doesn't let you use variables on
> > > the ExecStart line of a service unit file so alternatives are required.
> > >
> > > The reason I'm being very careful here this could set a precedent and at
> > > least for the launcher idea it'd require the usage of getenv() and execve(),
> > > and secure alternatives for these (secure_getenv(), execve_nosecurity())
> > > have either been merged or suggested before for Linux. The systemd discussion
> > > is only specific to Linux but if we have a launcher we could consider it for
> > > other supported OSes. All that said I'd like proper review of the security
> > > implications of *all* strategies but obviously in particular the launcher
> > > idea. I want to tread carefuly before setting precedents.
> >
> > You can also just invoke a shell script from ExecStart=. I mean, we try
> > to deemphesize them in the boot process, but there's nothing wrong with
> > using shell, if you need to parse shell configuraiton fragments and just
> > want to execute on ot another program...
>
> I tried this and it didn't work given that systemd expects sd_notify()
> to be called from the parent process, in this case the shell script.
Hmm? You should "exec" the real daemon binary at the end, not just fork
it off. That wait the shell script process is replaced by the daemon
binary, which is what you want.
Lennart
--
Lennart Poettering, Red Hat
On Thu, Jun 05, 2014 at 01:22:13PM +0200, Lennart Poettering wrote:
> On Thu, 05.06.14 02:31, Luis R. Rodriguez ([email protected]) wrote:
>
> > On Sun, Jun 01, 2014 at 08:15:47AM +0200, Lennart Poettering wrote:
> > > On Fri, 30.05.14 01:29, Luis R. Rodriguez ([email protected]) wrote:
> > >
> > > > I'm cc'ing a few security folks as I'd appreciate review on the ideas here,
> > > > in particular that of a launcher idea on system to replace alternatives on the
> > > > ExecStart= line of a systemd service unit file, alternative ideas are of
> > > > course welcomed. I'm also Cc'ing systemd-devel as this subject was reviewed
> > > > a little while ago with nothing concrete being recommended but instead a few
> > > > options being now archived as possibilities. I'm looking for a bit wider
> > > > review of the approaches and recomendations.
> > > >
> > > > Some general background for non xen folks: old xen requires the launch of
> > > > a daemon which implements supports of the xenstore, which is the database
> > > > that xen uses for information about guests / dom0. There are two supported
> > > > daemons, xenstored (C version) and oxenstored (Ocaml version) but they do the
> > > > same thing. Right now old init lets you override which one you pick through
> > > > an environment variable on /etc/{sysconfig,default}/xencommons, the script
> > > > will use the appropriate on there. Systemd doesn't let you use variables on
> > > > the ExecStart line of a service unit file so alternatives are required.
> > > >
> > > > The reason I'm being very careful here this could set a precedent and at
> > > > least for the launcher idea it'd require the usage of getenv() and execve(),
> > > > and secure alternatives for these (secure_getenv(), execve_nosecurity())
> > > > have either been merged or suggested before for Linux. The systemd discussion
> > > > is only specific to Linux but if we have a launcher we could consider it for
> > > > other supported OSes. All that said I'd like proper review of the security
> > > > implications of *all* strategies but obviously in particular the launcher
> > > > idea. I want to tread carefuly before setting precedents.
> > >
> > > You can also just invoke a shell script from ExecStart=. I mean, we try
> > > to deemphesize them in the boot process, but there's nothing wrong with
> > > using shell, if you need to parse shell configuraiton fragments and just
> > > want to execute on ot another program...
> >
> > I tried this and it didn't work given that systemd expects sd_notify()
> > to be called from the parent process, in this case the shell script.
>
> Hmm? You should "exec" the real daemon binary at the end, not just fork
> it off. That wait the shell script process is replaced by the daemon
> binary, which is what you want.
I tried both just running it and also running exec foo; both presented
the same issue given that shell exec does not really execve.
Luis
On Thu, 05.06.14 20:01, Luis R. Rodriguez ([email protected]) wrote:
> > Hmm? You should "exec" the real daemon binary at the end, not just fork
> > it off. That wait the shell script process is replaced by the daemon
> > binary, which is what you want.
>
> I tried both just running it and also running exec foo; both presented
> the same issue given that shell exec does not really execve.
Hmmm? You shell's "exec" command doesn't actually execve()? What are you
using? This doesn't sound very accurate...
Lennart
--
Lennart Poettering, Red Hat
On Thu, Jun 5, 2014 at 12:24 PM, Lennart Poettering
<[email protected]> wrote:
> On Thu, 05.06.14 20:01, Luis R. Rodriguez ([email protected]) wrote:
>
>> > Hmm? You should "exec" the real daemon binary at the end, not just fork
>> > it off. That wait the shell script process is replaced by the daemon
>> > binary, which is what you want.
>>
>> I tried both just running it and also running exec foo; both presented
>> the same issue given that shell exec does not really execve.
>
> Hmmm? You shell's "exec" command doesn't actually execve()? What are you
> using? This doesn't sound very accurate...
$ strace -e execve /bin/sh -c 'exec /bin/echo test'
execve("/bin/sh", ["/bin/sh", "-c", "exec /bin/echo test"], [/* 54 vars */]) = 0
execve("/bin/echo", ["/bin/echo", "test"], [/* 54 vars */]) = 0
test
+++ exited with 0 +++
I get similar results on Ubuntu using dash.
--Andy
On Wed, Jun 04, 2014 at 07:52:56PM -0700, Cameron Norman wrote:
> On Wed, Jun 4, 2014 at 5:31 PM, Luis R. Rodriguez <[email protected]> wrote:
> > On Sun, Jun 01, 2014 at 08:15:47AM +0200, Lennart Poettering wrote:
> >> On Fri, 30.05.14 01:29, Luis R. Rodriguez ([email protected]) wrote:
> >>
> >> > I'm cc'ing a few security folks as I'd appreciate review on the ideas here,
> >> > in particular that of a launcher idea on system to replace alternatives on the
> >> > ExecStart= line of a systemd service unit file, alternative ideas are of
> >> > course welcomed. I'm also Cc'ing systemd-devel as this subject was reviewed
> >> > a little while ago with nothing concrete being recommended but instead a few
> >> > options being now archived as possibilities. I'm looking for a bit wider
> >> > review of the approaches and recomendations.
> >> >
> >> > Some general background for non xen folks: old xen requires the launch of
> >> > a daemon which implements supports of the xenstore, which is the database
> >> > that xen uses for information about guests / dom0. There are two supported
> >> > daemons, xenstored (C version) and oxenstored (Ocaml version) but they do the
> >> > same thing. Right now old init lets you override which one you pick through
> >> > an environment variable on /etc/{sysconfig,default}/xencommons, the script
> >> > will use the appropriate on there. Systemd doesn't let you use variables on
> >> > the ExecStart line of a service unit file so alternatives are required.
> >> >
> >> > The reason I'm being very careful here this could set a precedent and at
> >> > least for the launcher idea it'd require the usage of getenv() and execve(),
> >> > and secure alternatives for these (secure_getenv(), execve_nosecurity())
> >> > have either been merged or suggested before for Linux. The systemd discussion
> >> > is only specific to Linux but if we have a launcher we could consider it for
> >> > other supported OSes. All that said I'd like proper review of the security
> >> > implications of *all* strategies but obviously in particular the launcher
> >> > idea. I want to tread carefuly before setting precedents.
> >>
> >> You can also just invoke a shell script from ExecStart=. I mean, we try
> >> to deemphesize them in the boot process, but there's nothing wrong with
> >> using shell, if you need to parse shell configuraiton fragments and just
> >> want to execute on ot another program...
> >
> > I tried this and it didn't work given that systemd expects sd_notify()
> > to be called from the parent process, in this case the shell script.
>
> Just use exec before the daemon command. I am pretty certain it can be
> just like this:
>
> ExecStart=/bin/sh -c "exec $XENSTORED"
>
> xenstored then has the same PID as the sh process, and $NOTIFY_SOCKET
> works just fine.
Actually this does work on a test unit I just built. I'll proceed with
this approach since I haven't heard back from others and I think
this is the best approach now.
Luis